Office and ambulatory blood pressure (BP) measurements are the main techniques to detect the effects of antihypertensive treatments in clinical trials, but the treatment-induced changes in these BP values can differ markedly. We performed a meta-analysis of clinical trials to quantify these differences and identified some of the associated factors.
We conducted a MEDLINE search for randomized clinical trials (RCTs) on hypertensive patients treated with at least one antihypertensive drug that reported changes in both office and 24-h BP. Random-effects models were fitted to estimate the summary of the difference between the changes as quantified by either technique. The I2 and Cochrane's Q statistics were calculated to evaluate the heterogeneity between studies.
A total of 52 studies were included in our meta-analysis with about 9500 patients. The summary estimate Δ of SBP and DBP was −6.5 (95% confidence interval: −7.5 to −5.6) and −3.3 (95% confidence interval, −3.9 to −2.7), respectively. The difference was independent on the treatment duration and use of mono or combination treatment but for SBP it varied with the different treatment types in monotherapy, and it was greater in relation to baseline office BP and age. Allowing for the placebo effect also reduced the difference. Absolute on treatment BP values were at target for either pressure and the rate of controlled hypertensive individuals was similar (around one-third) for either measuring approach.
Our meta-analysis confirms that overall treatment-induced reduction is markedly greater for office BP than for 24-h BP, but it also shows that the quantitative relationship between these two measuring approaches varies with demographic, clinical and therapeutic conditions as well as in relation to placebo correction.